Obstructive sleep apnea syndrome (commonly referred to as obstructive sleep apnea, sleep apnea syndrome, and/or sleep apnea) is a medical condition that includes repeated, prolonged episodes of cessation of breathing during sleep. During a period of wakefulness, the muscles of the upper part of the throat passage of an individual keep the passage open, thereby permitting an adequate amount of oxygen to flow into the lungs. During sleep, the throat passage tends to narrow due to the relaxation of the muscles. In those individuals having a relatively normal-sized throat passage, the narrowed throat passage remains open enough to permit the adequate amount of oxygen to flow into the lungs. However, in those individuals having a relatively smaller-sized throat passage, the narrowed throat passage prohibits the adequate amount of oxygen from flowing into the lungs. Additionally, a nasal obstruction, such as a relatively large tongue, and/or certain shapes of the palate and/or the jaw of the individual, further prohibit the adequate amount of oxygen from flowing into the lungs.
An individual having the above-discussed conditions can stop breathing for one or more prolonged periods of time (e.g. ten seconds or more). The prolonged periods of time during which breathing is stopped, or apneas, are generally followed by sudden reflexive attempts to breathe. The reflexive attempts to breathe are generally accompanied by a change from a relatively deeper stage of sleep to a relatively lighter stage of sleep. As a result, the individual suffering from obstructive sleep apnea syndrome generally experiences fragmented sleep that is not restful. The fragmented sleep results in one or more of excessive and/or inappropriate daytime drowsiness, headache, weight gain or loss, limited attention span, memory loss, poor judgment, personality changes, lethargy, inability to maintain concentration, and/or depression.
Other medical conditions can also prevent individuals, including adults and infants, from receiving the adequate amount of oxygen into the lungs. For example, an infant who is born prematurely can have lungs that are not developed to an extent necessary to receive the adequate amount of oxygen. Further, prior to, during and/or subsequent to certain medical procedures and/or medical treatments, an individual can be unable to receive the adequate amount of oxygen. Under these circumstances, it is known to use a ventilation interface to apply a positive pressure to the throat of the individual, thereby permitting the adequate amount of oxygen to flow into the lungs. In the known ventilation interface, oxygen and/or room air containing oxygen is delivered through the mouth and/or nose of the individual. Existing types of positive pressure applied by the known ventilation interface include continuous positive airway pressure (CPAP), in which a positive pressure is maintained in the throat passage throughout a respiratory cycle, bi-level positive airway pressure (BiPAP), in which a relatively high positive pressure is maintained during inspiration and a relatively low positive pressure is maintained during expiration, and intermittent mechanical positive pressure ventilation (IPPV) in which a positive pressure is applied when apnea is sensed (I.e., the positive airway pressure is applied intermittently or non-continuously).
One conventional ventilation interface for the application of positive pressure includes a face mask that covers both the nose and the mouth. See, for example, U.S. Pat. No. 4,263,212 to Mizerak and U.S. Pat. No. 6,123,071 to Berthon-Jones et al. Other face masks include configurations that cover only the nose or only the mouth. Standard masks have air supplied under pressure and use headgear or harnesses configured at least with what is referred to as a lip strap, thereby preventing air from escaping from the user's mouth. Such a strap is positioned level the patient's lips and wasp circumferentially around the patient's head from one side of the mask to the other. To keep the supply of positive gas pressure and to maintain the required seal that prevents the gas supply from leaking, a force must be applied to the head of the individual. As a result, the harness is generally uncomfortable to wear, particularly when sleeping. The applied pressure often results in undesirable irritation and sores caused by movement of the mask and harness during periods of both wakefulness and sleep. Further, the required seal is generally difficult to maintain when the mask and harness is moved.
The force that the harness applied to the mask against the face also applies an undesirable pressure to the sinus area adjacent to the nose, causing the nasal sinus airways to narrow. This narrowing causes an increase in the velocity of flow through the upper anatomical airways and a decrease in the lateral pressure against the nasal mucosal wall. Additionally, if the tubing between the mask and the gas supply unit folds undesirably, this problem will be exacerbated. The above-discussed combination of increased flow velocity and decreased pressure results in the removal of moisture form the mucosal walls during inspiration and may cause an undesirable drying and a burning sensation within the nares. As a result, the individual may remove the mask to alleviate these discomforts, consequently discontinuing the beneficial application of the positive pressure. Such increased air flow velocity and decreased pressure deteriorate the laminar flow between the air input and output portions of the conventional mask.
A common complaint of a patient regarding ventilation masks is that they cause claustrophobia. Such masks have large headgear that wrap around the entirety of the user's head and cover a significant area of the face including the periphery of both the nose and the mouth. Additionally such masks have a large amount of dead space within the mask where gas can be re-breathed by a patient, and a large area against the face of a user that must be sealed against the mask.